98
WGN, the Journal of the IMO 37:4 (2009)
Ongoing meteor work
A Comprehensive List of Meteor Showers Obtained from 10 Years of
Observations with the IMO Video Meteor Network
Sirko Molau
1
and Jürgen Rendtel
2
We have analysed data of more than 450 000 video meteors recorded over more than 10 years in the IMO Video
Network. The single station data cover all Solar longitudes and allow to derive positions of radiants and the
corresponding velocities as well as activity information for meteor showers. We present results for 9 major
showers, 44 minor showers and 12 new detections. Shower data are compared with the entries kept by the IAU
Meteor Data Center. For some showers we find a systematic shift of the velocity during the activity period.
Received 2009 August 10
1
Introduction
Video meteor observations have significantly increased
our knowledge about meteor showers over the recent
years. Whereas first observations of amateurs with
image-intensified cameras date back to the 1980s, it
was the shift towards automated observation that paved
the road for the breakthrough of this technique. For
over ten years now, video observers from several countries have collected video meteors in the same fashion
and created an unprecedended database of more than
450 000 single station video meteors to date. Starting
in 2005, automated statistical analysis procedures were
developed to extract reliable meteor shower information
from the database. First results were presented by Molau (2006 and 2008). Earlier this years, results from
the Japanese SonotaCo network were published (SonotaCo, 2009). They represent an independent data set
which is analyses based on different analysis algorithms
(double-station) and software (UFO* tool set). The
results obtained by SonotaCo were in good agreement
with our findings, which proved the maturity of our
analysis technique and encouraged us to carry out a new
analysis. This time, the automated shower extraction
was only the first step. The results for each shower were
manually checked and refined. Weak shower detections
with strong scatter in radiant position or shower velocity were omitted; showers that were artificially split by
the analysis software were joined. We compared the detected shower with the compilation of radiants (Jopek,
2009) in the IAU Meteor Data Center (called MDC list
hereafter) and recalculated meteor shower parameters
(radiant position and drift, activity interval, meteor
shower velocity and activity) after rejecting outliers.
The result is a comprehensive list of 65 meteor showers
obtained from over ten years of observations in the IMO
video network.
In this paper we first introduce the IMO Video Meteor Network, which provided the observational basis
for this anaylsis. Then we describe the data set and
1 Abenstalstr. 13b, 84072 Seysdorf, Germany.
Email: [email protected]
2 Eschenweg 16, 14476 Marquardt, Germany.
Email: [email protected]
IMO bibcode WGN-374-molau-videoshowers
NASA-ADS bibcode 2009JIMO...37...98M
give an outline of the analysis algorithm. We describe
the analysis of selected showers in detail to demonstrate
what can be achieved with the data. Thereafter, the detected meteor showers are presented and discussed. We
start with nine major well-known showers to explore the
limits, when their signal is strong enough to stand out
of the sporadic background. Next we concentrate on
minor showers, which are marked as established in the
MDC list. Moving further towards the detection limit,
we present minor showers from the MDC list, who have
a working status but could be confirmed by our analysis. Next we list a set of new showers that were obtained from the IMO Video Meteor Database. For each
shower, we give the interval of activity, radiant position
and drift, meteor shower velocity, the maximum video
rate (a measure of the meteor shower activity similar
to the visual ZHR) as well as an activity profile. We
also state, how many single station meteors from the
IMO database were attributed to the meteor shower.
Finally we report on short-duration showers from the
MDC list, which were only detected after we relaxed the
minimum meteor shower duration criterion, and finally
we present and discuss those showers that are marked
as established in the MDC list, but cannot be detected
in our database.
In this paper, we leave out results concerning the
Antihelion source (except the Taurid branches) as well
as sporadic sources (e.g. Apex and Antapex source).
These are frequently detected in the video data, but
their analysis deserves special care, because they have
large radiation areas and stronger scatter in velocity.
We also note that there is a complex of radiants in
Perseus and Auriga in September/October, which needs
special treatment to identify the individual branches.
All of these will be subject of aditional analyses presented in the future.
Throughout the paper, we use the MDC numbers
and three-letter codes for the showers. For convenience,
we also give the shower designations in the respective
sections.
2
The IMO Video Meteor Network
The continuous monitoring of the night sky by video
meteor cameras started with a first station in Aachen
(Germany) in March 1999 (Molau, 2001). Other ob-
WGN, the Journal of the IMO 37:4 (2009)
99
Figure 1 – Fields of view of the IMO network cameras in Central Europe as of December 2008.
servers joined the AKM network (Arbeitskreis Meteore,
AKM), and by the end of 1999, five German observers
had collected over 8 000 meteors within 1 000 hours of
effective observing time. In the following years, the network grew steadily, and by 2004 it was renamed to IMO
Video Meteor Network because of its international character.
The common characteristic of all observers in the
IMO network is the use of the MetRec software (Molau, 1998). The PAL/NTSC signal of the video camera
is directly fed into the analysis PC, digitized with a
Matrox Meteor II framegrabber, and inspected by the
MetRec software in real-time. Once a meteor is detected, astrometric and photometric routines are applied. The position, brightness and velocity of each meteor are stored together with a sum image and a short
time-sequence of the event. All observers send their
data on a monthly basis to the IMO video commission,
where they are quality-checked, corrected if necessary,
analyzed, archived and published.
Right from the start, the IMO Network focused on
single station observation. The major advantage is, that
each observer with the right equipment can participate
in the network and provide useful data, no matter how
many cameras there are in his part of the world. There
is no need to synchronize the fields of view and technical parameters of individual cameras for double station
work. Each meteor contributes to the analysis independently where and when it was observed, whether there
are other recordings from the same event or how the ob-
serving geometry looks like. On the other hand, meteor
trajectories and orbits cannot be determined directly
from single station data. It requires large data sets and
sophisticated statistical algorithms to reveal not only
the radiant position of meteor showers, but also their
pre-atmospheric entry velocity, the interval of activity
and activity profiles with high precision.
Two types of video cameras are most popular these
days. On the one hand, there are non-intensified
Mintron and Watec cameras with Sony ExView HAD
chip as sensor, typically equipped with f /0.8 Computar
c-mount lenses of 3.8, 6, or 8 mm focal length. Their
field of view ranges between 40 and 80◦ with limiting
magnitudes between +3 and +4 mag. On the other
hand, there are a few image-intensified cameras. Most
popular is the Philips XX-1332 second generation image intensifier tube (or other brands of the same device)
with 50 mm photo cathode. In connection with a f =
50 mm f /1.4 standard photographic lens, it achieves a
field of view of roughly 60◦ at limiting magnitudes beyond +6 mag. Under dark skies, image-intensified cameras record on average about a factor of three more meteors than non-intensified cameras, but they are more
delicate and therefore difficult to handle in automated
systems.
Over the years, the degree of automation has increased significantly in the IMO network. In the beginning, the cameras were manually started in clear nights.
Nowadays, most cameras are operated fully automated.
They are activated by a time switch in the evening and
100
WGN, the Journal of the IMO 37:4 (2009)
Figure 2 – Effective observing time of the IMO Video Meteor
Network 1999–2008.
Figure 4 – Distribution of meteors over Solar longitude.
Due to overlapping sliding intervals, each meteor contributes
twice.
gives an overview of all observers contributing more
than ten observing nights to the video database. We are
grateful to their passion, which enabled the collection of
this to-date unprecedented data set of high-quality meteor recordings in the optical domain, completely covering all solar longitudes.
Figure 3 – Number of meteors recorded by the IMO Video
Meteor Network 1999–2008.
shut down automatically in the morning. Thus, they
cover meteor activity at any time with clear skies. Also
the size of the network has extended significantly over
the last ten years. Most parts of Central Europe are
well covered (Figure 1), and two cameras are operated
in North America.
Thanks to the network size and the high degree of
automation, the amount of data and their quality have
increased significantly over the recent years. In 2008,
24 observers from ten countries contributed to the network with overall 37 cameras (Molau & Kac, 2009).
They recorded more than ten times as many meteors
within twenty times as many observing hours than in
1999. Between 2006 and 2008, there was just a single
night without a meteor record because of poor weather
at all sites. Figure 2 shows the total effective observing time in the IMO Video Meteor Network, and Figure 3 the number of meteors recorded each year. Until
mid-2009, more than 30 observers from twelve countries
(Australia, Czech Republic, Finland, Germany, Hungary, Italy, Portugal, Slovenia, Spain, the Netherlands,
UK, and the USA) submitted their data.
3
Data set and analysis procedure
The analysis presented here is based on all data collected by the IMO network until June 2009. Thus, beside the main data set 1999–2008, also roughly 5 000
meteors recorded before the start of the network (1993–
1998) and 31 000 meteors from the first half of 2009 were
included. The resulting data set consists of 451 282 single station meteors recorded in 3 363 observing nights
and 107 594 hours of effective observing time. Table 1
Figure 4 depicts the distribution of meteors over Solar longitude. The analysis was based on sliding intervals of two degrees length and one degree shift, so each
meteor contributed to two consecutive solar longitude
intervals. The times of the major showers with up to
16 000 meteors per interval are clearly visible. But also
times of low meteor shower activity are well covered
– there is no single interval with less than 680 meteor
records. The average is close to 2 500 meteors per interval.
The procedure used to analyze this data set has been
applied first to a smaller subset in 2006 (Molau, 2006).
It was refined in a second analysis (Molau, 2008). Here
we give a short summary of the algorithms.
For each meteor, the time and place of observation
as well as the coordinates of the start and end point
and the angular velocity are given. Meteor shower radiants are described by four parameters: their position
(right ascension α and declination δ), velocity at infinity V∞ , and the Solar longitude λ⊙ . For each pair
of meteor m and radiant r, a conditional probability
P (m|r) can be calculated. It describes the probability, that the meteor belongs to the (zenith attraction
corrected) radiant. The conditional probability is computed from two measures – the distance d (in ◦ ) at which
the backward prolongation of the meteor misses the radiant, and the difference v (in ◦ /s) between the expected
and the observed angular meteor velocity. The expected
angular velocity that a meteor from radiant r would
have at the position of m, is calculated on the basis of
the average meteor altitude, which was recently refined
(Molau & SonotaCo, 2009). Both the radiant miss distance and the angular velocity difference are combined
in a three-dimensional Laplacian probability distribution. The type of distribution and its parameters were
obtained from data (Molau, 2008) and reflect typical
video observation errors:
WGN, the Journal of the IMO 37:4 (2009)
101
Table 1 – Observers who contributed more than 10 observing nights to the IMO Video Meteor Network.
Observer
Sirko Molau
Jörg Strunk
Javor Kac
Ilkka Yrjölä
Stane Slavec
Flavio Castellani
Orlando Benitez-Sanchez
Jürgen Rendtel
Bernd Brinkmann
Detlef Koschny
Mihaela Triglav
Robert Lunsford
Enrico Stomeo
Stephen Evans
Wolfgang Hinz
Carl Hergenrother
Steve Quirk
Rui Goncalves
Stefano Crivello
Biondani Roberto
Mirko Nitschke
David Przewozny
Stefan Ueberschaer
Maurizio Eltri
Ulrich Sperberg
Paolo Ochner
Rosta Stork
Rob McNaught
Andre Knöfel
Klaas Jobse
Mitja Govedič
Antal Igaz
Miloš Weber
other
Overall
Country
IMO
Code
Nights
Eff. obs. time
[h]
Meteors
DE
DE
SL
FI
SL
IT
ES
DE
DE
NL
SL
US
IT
UK
DE
US
AU
PT
IT
IT
DE
DE
DE
IT
DE
IT
CZ
AU
DE
NL
SL
HU
CZ
MOLSI
STRJO
KACJA
YRJIL
SLAST
CASFL
BENOR
RENJU
BRIBE
KOSDE
TRIMI
LUNRO
STOEN
EVAST
HINWO
HERCA
QUIST
GONRU
CRIST
ROBBI
NITMI
PRZDA
UEBST
ELTMA
SPEUL
OCHPA
STORO
MCNRO
KNOAN
JOBKL
GOVMI
IGAAN
WEBMI
2344
1696
1173
942
871
794
733
647
598
509
505
495
492
457
455
399
341
320
229
229
213
196
173
169
159
134
98
52
47
47
33
32
29
25
20 807.2
12 709.4
10 333.0
5 419.2
4 318.9
5 775.4
4 088.3
3 823.4
2 376.2
3 126.3
2 585.9
3 204.2
3 605.5
2 807.3
2 689.5
2 805.7
3 041.8
2 850.6
1 459.4
1 261.6
942.5
1 073.6
882.3
1 210.4
1 021.6
733.2
1 052.8
401.2
289.0
288.0
156.7
217.7
49.4
186.8
127 072
42 009
31 354
18 596
11 262
13 802
10 473
17 223
8 366
11 567
8 474
22 122
13 854
11 411
13 690
5 570
10 109
9 931
6 217
4 082
5 425
3 745
1 684
5 886
4 339
1 763
14 732
5 285
648
2 231
489
369
1 050
6 452
3363
107 594.0
451 282
102
WGN, the Journal of the IMO 37:4 (2009)
P (m|r) = exp(−0.8 × d) × exp
−v
.
0.4 + v/50
Based on the conditional probability, a search for
possible meteor shower radiants is carried out, which is
the computationally most demanding part of the analysis. At first the data set is cut into Solar longitude
slices (two degrees length, one degree shift). For each
Solar longitude interval, an iterative search procedure
is carried out.
At initialization, the probability of each possible radiant point (position in steps of 0 ◦. 5, velocity at infinitiy
in steps of 1 km/s) is accumulated over all meteors of
the interval. The probability distributions of individual
meteors are not normalized, i.e. the most probable radiant gets a value of 1.0 and the probability mass provided
by each meteor differs. In the iterative phase, the radiant with highest accumulated probability is selected.
According to standard criteria for meteor shower assignment, all meteors belonging to that radiant are determined and taken out of the data set. Their probability
distribution is calculated and subtracted from the overall distribution. Then the next iteration is carried out
to extract the next strongest radiant. The procedure
terminates after 50 iterations. To avoid interference of
nearby radiants, the meteor shower assignment is repeated once all radiants are determined (Molau, 2008).
After the most probable radiants are determined for
each solar longitude, similar radiants in consecutive Solar longitude intervals are connected to identify meteor
showers. The showers are compared against the current
MDC list (Jopek, 2009) to classify known showers. The
main parameters that determine the number and quality of detected meteors showers are the minimum number of intervals with suitable radiants (minimum meteor
shower duration: 5◦ in Solar longitude), the maximum
position difference (7◦ ) and the maximum velocity difference (7 km/s) between the radiants from one Solar
longitude interval to the next. In brackets are the figures use primarily for this analysis.
Once the meteor showers were determined, their basic parameters (activity interval and date of maximum
activity, radiant position and drift, average velocity)
were calculated. To compute the meteor shower activity
is in particular challenging, as the data set was a mixture of observations from different cameras with different lenses under different observing conditions. Neither
the effective observing time nor the field of view nor
limiting magnitude per Solar longitude were known. At
first, the observation probability (Molau, 2008) was applied to each meteor that belongs to a detected radiant.
This probability is the average of the sine of the radiant altitude at night time in the given solar longitude
interval. A meteor from a hypothetical radiant that
is all night long at zenith would get a weight of 1.0,
whereas a meteor from a radiant that is visible for only
a short time near the horizon would get a weight of up
to 100. This way, the geometric observing conditions
are corrected – typical observability function weights
at mid-northern latitude range between 1.5 for easily
visible Geminids and 30 for the difficult to observe ηAquariids.
In the next step, all meteors that belong to showers
are counted, and all remaining meteors are declared as
sporadics. The meteor shower activity (called video rate
VR hereafter) at a certain Solar longitude is now the ratio between the observability function corrected number
of shower meteors and the number of sporadics in that
interval. This way, the difference in effective observing
time, field of view diameter and limiting magnitude is
accounted for.
Finally, the video rate is scaled and corrected for
the annual sporadic activity variation. It was found
that the sporadic activity in the Northern hemisphere
can be approximated by a sine shaped function with a
minimum of 2.2 meteors per hour at Solar longitude
350◦ and a maximum of 4.2 at 170◦ (Molau, 2008).
The scaling factor was initally chosen such that the ηAquariids yield a maximum VR of 50. It turned out,
that the video rate VR resembles the long-term ZHR
of a shower remarkably well. Thus, we are confident
that we can not only give a qualitative account of meteor shower activity (shape of the activity profile and
time of the maximum), but also a quantitative estimate
of the ZHR. Due to the 2-day-intervals, however, the
peaks are significantly smoothed out and therefore below the peak ZHRs derived from short intervals.
4
Manual refinement
All automatically detected showers were manually
checked. When the video rate of a shower falls below
one, the sporadic dilution becomes dominating. For this
reason, there are typically a few uncertain intervals at
the begin and end of each shower activity period, which
are affected by chance alignments with sporadic meteors. We reduced the activity intervals of each shower
to those with radiant position and velocity fitting well
to the average shower parameters. We corrected cases,
where one shower was cut into two, and we omitted
showers, which contained only few meteors and showed
strong scatter from one solar longitude interval to the
next.
To account for meteor showers of shorter duration,
we repeated the meteor shower search with reduced
minimum meteor shower duration of four and three
degrees in Solar longitude. Naturally, the number of
possible showers grew significantly, so we focused on
those which were not found in the previous analysis with
longer duration, and which fitted well to showers from
the MDC list.
In the next steps, the meteor shower parameters
were refined. The position and drift of the radiant
was re-calculated in the possibly reduced Solar longitude interval by a weighted linear regression, with the
absolute meteor counts per interval taken as weight.
For major showers, the Solar longitude of the maximum
activity was re-calculated as the weighted mean Solar
longitude, using only the intervals of highest activity
with the video rate as weight. The meteor shower velocity was refined as well. It is the average over all Solar
WGN, the Journal of the IMO 37:4 (2009)
103
longitude intervals. Here, each value was weighted by
the meteor number. This allows us to report both the
Solar longitude (i.e. date) of the shower maximum and
the velocity rounded to the nearest 0.1 degree or km/s,
respectively, even though the underlying analysis was
carried out for steps of 1 degree in solar longitude and
1 km/s in velocity V∞ .
We estimate that the accuracy of the radiant position is better than 1◦ if the activity VR ≥ 2, and the
average velocity at infinity is accurate to 1 km/s for all
showers.
5
Meteor shower velocities
When calculating the radiant position and drift for long
duration meteor showers, we noted that in some cases
the meteor shower velocity did not only show some arbitrary scatter around the average value, but that the calculated velocity increased or decreased systematically
over the activity period. At first we did not pay special
attention to this observation, because we assumed that
to be an artefact of the analysis procedure. However,
on our request, the Japanese meteor observer SonotaCo checked his data set of meteoroid orbits obtained
from the SonotaCo video network (SonotaCo, 2009) and
found similar variations. Even more, for all four showers
which have been compared in detail (ETA, PER, SDA
and ORI), he reported exactly the same behaviour (decreasing, constant or increasig velocity) with only little
deviation in the amount of the velocity change.
As both data sets and analysis procedures are completely independent, we conclude that the observed variations in meteor shower velocity over time are real. For
this reason, we add the detected variation in velocity
(in km/s per degree in Solar longitude) for all major
and long-lasting showers with sufficient data. We found
that LYR, ETA, and KCG are showers with a particularly large increase in velocity over time, whereas SDA,
QUA, CAP, NOO and JPE show considerable velocity
decreases.
As the Earth crosses different sections of the meteoroid stream over a longer period which have undergone
numerous and variable orbit perturbations, these variations need to be correlated with the Earth-meteoroid
collision geometry. For example, we find that the shift
is in the opposite direction for the Orionids and the
η-Aquariids, and larger in the latter case. As the showers represent different cross-sections through the same
meteoroid stream with the Orionids being the far more
distant path from the centre, the numbers listed in Table 2 indicate that this effect may also be related to
different ejection speeds from the parent comet. However, at this time we have no proven explanation for the
observed velocity changes.
Figure 5 – Radiant of the Orionids derived from the video
data. The shaded (grey) parts at the outer edges of the
drift path show the position found from the data which were
excluded because of the position uncertainties.
MDC list distinguishes between showers that are established and those which have a working list status,
labelled ’e’ and ’w’, respectively. The Toroidal, Apex
and Antihelion sources also occur in our data set. In
this paper, we concentrate on showers which are linked
to neither of these permanent sporadic and ecliptical
soures (except the Northern and Southern Taurids),
because the analysis method was adjusted for showers
with compact radiants. Sources with diffuse radiation
areas would need to be treated in a different way in an
extra paper. Another complex which we found deserves
a detailed separate analysis is the set of showers radiating from the Perseus-Auriga region from end-August
to mid-October. Of these showers, we only list the Aurigids and the September ε-Perseids here.
6.1
Major showers
The nine meteor showers with the highest activity level
have been used for testing and calibrating the detectability of radiants from the data sample. We present
details for the Orionids and the Quadrantids, because
our results extend beyond the confirmation of their radiant position and drift and their activity level. In both
cases, our data indicate a longer period in which the
activity and the radiant can be clearly detected. Our
activity profiles are from data collected over about a
decade and for the search algorithm we also bin over
an interval length of 2◦ in Solar longitude. For these
reasons, our profiles are smoother than the graphs calculated from short binning intervals, and the peak level
of the VR remains well below the peak ZHRs listed for
the showers.
The Orionids can be observed from both hemispheres. The date of the peak as well as the radiant
6 Application of the method and
position and drift found from our data agree perfectly
results of radiant searches
with the data stored in the MDC list. When we look
First of all, our data provides us with a detailed set of at the outer edges of the shower activity, we find that
information about all major showers, such as their ac- the radiant can be continuously followed towards earlier
tivity period and their radiant position and drift. The and later Solar longitudes (Figure 5). Both the video
104
WGN, the Journal of the IMO 37:4 (2009)
Figure 6 – Radiant of the Quadrantids derived from the
video data. In this case the position becomes uncertain in
the outer bins.
rate VR (shown in Figure 8) and the steady shift of the
radiant position in combination with the same velocity of the meteoroids leads to an activity period which
extends from end-September to November. Both parameters limit the detectability of the activity from a
radiant.
Our video rate calibration is based on the η-Aquariids. The comparison between the VR and the longterm ZHR allows us to set a detection limit of VR = 0.7.
The other limit is the reliability of the radiant position.
The lower the number of true shower meteors is, the
larger is the amount of sporadic meteors accidentially
lining up with the radiant (and fitting the velocity). As
a result of the sporadic effect, the calculated position
will become uncertain and the radiant deviates from the
position calculated for the neighbouring bin as shown
for the Orionids in Figure 5. If these differences exceed
3◦ in neighbouring bins, we do not regard this as the
signal of a detectable shower. These limits have been
generally applied to all detections later. Conclusion:
the detection of showers from the current data sample
is possible if VR ≥ 0.7 and (∆α, ∆δ) ≤ 3◦ per 1◦ in
Solar longitude.
The Quadrantids show peak rates which are among
the strongest of all showers currently observable from
the Earth. Usually, the shower activity is assumed to
start on January 1 and to cease by January 6. Again,
our analysis shows a perfect agreement in the complete
data set for the near-peak period. Moreover, the activity obviously extends in both directions. We detect
meteors from the region associated to the Quadrantids
from λ⊙ =274◦ (December 27) to 292◦ (January 12) with
VR > 0.9 all the time. As shown in Figure 6, the
recorded meteors do not define a reliable radiant before
281◦ and after 290◦ . Hence we give the Quadrantid activity period as λ⊙ = 281◦ − 290◦ , here limited by the
consistency of the radiant drift, although the averaged
drift after 290◦ is still consistent with the period before
this date. Whether the radiant becomes diffuse or this
is just an effect of the small sample, cannot be decided
from our analysis method.
Figure 7 – Radiant of the Perseids derived from the video
data. Towards the ends, the radiant position becomes unreliable.
The complete list of data obtained from the most
active showers are summarized in Table 2 and compared
with the MDC list entries. Graphs representing the
activity in terms of VR are shown in Figure 8.
6 LYR (Lyrids): we find VR ≥ 0.6 for the entire
period 24–36◦; the radiant drift becomes inconsistent
only in the first and last bins – hence the period of
detectability is limited to 26–35◦. In this interval, the
VR is ≥ 0.7 (Figure 8).
31 ETA (η-Aquariids): the relative rate is VR ≥
4.0 between 36 and 61◦ . Rather few ETA meteors have
been recorded after May 18 (57◦ ) obviously due to the
shorter observing window at most observing locations.
Hence the radiant position starts to become inconsistent particularly after λ⊙ = 61◦ while it gives a smooth
drift for the entire period before this date. Our data
defines the shower over the interval 38 − 60◦ . The peak
rate was earlier used for calibrating the VR, hence, consistently, we find a maximum VR ≈ 54 (Figure 8). The
velocity shift of 0.12 km/s per 1◦ in Solar longitude
over the cross-section of the stream has been discussed
in Section 5. The shift during the ETA activity is larger
than in the Orionid period. The ETA meteoroids are
closer to the parent’s orbit and thus perhaps represent
a larger variation in the ejection conditions from the
inner to the outer regions of the stream.
7 PER (Perseids): we find VR > 4 even towards
August 30, but the radiant position calculated from the
video data varies after August 26 (Figure 7). From the
radiant data, we can trace the shower over the period
110–153◦ (July 13–August 26). In this case the variations of the derived radiant position in consecutive bins
exceed the threshold set for a reliable shower identification while the VR would be still well above the limit.
The large number of Perseids essentially in all bins also
causes additional detections in the vicinity of the Perseid radiant fitting velocity and radiant drifts similar
to that of the major shower. In all these cases, these
virtual radiants show very large scatter in their coordinates from one bin to the next (typically more than
3◦ ) being not parallel to the ecliptic, indicating that
these are artefacts. Similar effects need to be carefully
checked if detections during other major showers occur.
WGN, the Journal of the IMO 37:4 (2009)
105
14
31 ETA
50
6 LYR
12
40
10
VR
VR
8
30
6
20
4
10
2
0
0
26
28
30
32
Solar Longitude (J2000)
34
36
40
20
45
50
Solar Longitude (J2000)
55
60
70
7 PER
60
5 SDA
15
50
VR
VR
40
10
30
20
5
10
0
120
125
130
135
140
145
0
110
150
115
120
Solar Longitude (J2000)
70
60
125
130
135
140
145
150
Solar Longitude (J2000)
70
13 LEO
8 ORI
60
40
40
VR
50
VR
50
30
30
20
20
10
10
0
0
195
200
205
210
215
220
225
230
225
230
Solar Longitude (J2000)
235
240
245
Solar Longitude (J2000)
50
8
15 URS
4 GEM
7
40
6
5
VR
VR
30
20
4
3
2
10
1
0
252
254
256
258
260
262
264
Solar Longitude (J2000)
0
266
267
268
269
270
271
272
Solar Longitude (J2000)
10 QUA
20
VR
15
10
5
0
278
280
282
284
286
288
290
Solar Longitude (J2000)
Figure 8 – Activity profiles for the major showers derived from our video data sorted by the Solar longitude of their
occurrence (same as in Table 2).
WGN, the Journal of the IMO 37:4 (2009)
106
Table 2 – Data of the major meteor showers sorted by Solar longitude (J2000.0). (V) refers to the obtained video data, (L) gives the values of the MDC list. ∆V∞ is the observed
average velocity drift over the activity period in km/s per 1◦ in Solar longitude. Data Met. is the number of meteors from the shower in the video database
Shower
Peak λ⊙ [◦ ]
(V)
(L)
6 LYR
31 ETA
5 SDA
7 PER
8 ORI
13 LEO
4 GEM
15 URS
10 QUA
32.4
46.8
126.9
140.0
208.9
236.1
261.5
270.5
283.0
32
46
125
140
208
235
262
271
283
Period λ⊙ [◦ ]
(V)
(L)
26– 35
38– 60
118–150
111–153
191–232
223–248
252–265
266–272
281–290
26– 35
29– 67
110–146
114–151
189–224
227–241
255–265
265–274
–
Radiant position and drift [◦ ]
α
∆α
δ
∆δ
272.2
338.9
340.4
48.1
96.1
154.2
113.3
217.6
229.6
+0.57
+0.67
+0.86
+1.44
+0.78
+0.61
+0.96
+1.60
+0.59
+32.9
− 0.6
−16.4
+57.6
+15.5
+21.6
+32.2
+74.8
+49.5
−0.43
+0.32
+0.28
+0.25
+0.03
−0.29
−0.17
−0.13
−0.08
V∞ [km/s] and ∆V∞
(V)
(L)
46.2
66.8
43.6
59.0
67.3
70.6
35.0
32.6
42.2
+0.18
+0.12
−0.26
0
−0.06
0
0
–
−0.23
48.4
66.9
42.0
60.5
67.1
71.5
36.4
34.8
42.9
Max.
VR
Data
Met.
13
54
19
68
68
67
46
7
23
1516
1051
4716
22169
18249
9874
13193
1100
3184
Table 3 – Data of the established minor meteor showers sorted by Solar longitude (J2000.0); V and L refer to the values obtained from this video data analysis and taken from the
MDC list, respectively. If no activity period is in the list, we type ‘–’ in the respective column. The 32 DLM shower is listed here because of its connection to the 20 COM discussed
in the text. ∆V∞ is the observed average velocity drift over the activity period in km/s per 1◦ in Solar longitude. 0 indicates that no drift was observed, while ‘–’ means that no drift
can be derived because of too short duration or large scatter of data points.
Shower
145
1
191
12
206
208
17
2
22
18
250
16
19
20
32
319
331
ELY
CAP
ERI
KCG
AUR
SPE
NTA
STA
LMI
AND
NOO
HYD
MON
COM
DLM
JLE
AHY
Peak λ⊙ [◦ ]
(V)
(L)
50
125
137
141
158
167
231
197
210
230
248
254
256
264
268
281
280
49
127
137
145
158
170
224
224
209
231
245
265
260
268
274
283
286
Period λ⊙ [◦ ]
(V)
(L)
46– 53
109–138
132–146
134–146
156–162
161–171
206–258
165–237
203–214
223–248
230–254
244–269
255–268
260–271
253–315
280–285
279–289
42– 51
101–142
–
131–152
152–165
162–174
–
–
205–213
–
–
251–273
245–265
–
–
–
–
Radiant position and drift [◦ ]
α
∆α
δ
∆δ
291.1
305.1
43.2
285.9
90.7
47.2
59.7
31.7
160.8
22.8
91.9
123.9
99.2
174.5
161.5
146.6
125.9
+0.2
+0.57
+0.8
+0.6
+1.5
+0.7
+0.84
+0.85
+1.1
+0.2
+0.73
+0.80
+0.66
+0.65
+0.86
+0.6
+0.6
+43.2
−10.2
−11.0
+51.0
+39.3
+40.5
+22.7
+ 8.7
+36.4
+31.4
+15.2
+ 2.8
+ 8.1
+18.2
+30.5
+24.4
− 7.9
−0.0
+0.27
+0.4
+0.7
−0.4
+0.0
+0.15
+0.18
−0.2
+0.86
−0.03
−0.20
−0.15
−0.08
−0.43
−0.15
−0.14
V∞ [km/s] and ∆V∞
(V)
(L)
43.4
23.7
64.1
22.7
66.7
66.4
28.5
28.9
59.8
17.8
44.1
60.8
40.9
67.7
64.0
59.2
43.4
–
−0.18
–
+0.22
–
–
−0.09
−0.05
0
0
−0.22
−0.11
0
–
0
–
–
46.7
24.9
65
26.5
67
65.5
30.4
30.4
62.9
20.5
45.1
59.1
43.5
64.7
63.3
53.9
45.0
Max.
VR
Data
Met.
2.8
5.2
4.9
1.5
3.1
2.6
4.1
5.7
4.2
0.9
3.2
4.4
2.3
2.4
4.4
0.6
1.5
330
2283
513
864
392
1118
3946
8355
550
764
1219
1748
664
435
3181
119
187
WGN, the Journal of the IMO 37:4 (2009)
5 SDA (Southern δ-Aquariids): this is one of
the few strong southern showers with a symmetric maximum (VR = 19 at λ⊙ = 127◦ . We find a very long ‘tail’
of activity, but from 156◦(August 30) onwards, the radiant position becomes very uncertain with large scatter.
Additionally, VR < 2.0 after λ⊙ = 150◦ .
8 ORI (Orionids): the surprisingly high peak rate
of VR = 68 is mainly caused by the strong returns in
the years 2006 to 2008, which make up for more than
half of the overall data set. Contrary to the short peak
of the Perseids, the Orionid maximum is much wider.
As a result, the VR-profile suggests a shower similar
in strength to the Perseids. We find VR > 2 already
from 183◦ (September 26), but the radiant position is
quite variable until 190◦ (October 3). At 232◦ (November 15) we find VR < 2 and again a variable radiant
position in consecutive bins (see the remarks earlier in
this Section).
13 LEO (Leonids): VR > 2 for the entire period, and the radiant deviates from the smooth drift
only for the last bin (249◦ ). The varying positions of
Leonid peaks and storms over the entire decade cause
a relatively wide maximum although each of the individual peaks lasted only for about an hour or so.
In total, we can clearly detect Leonids in the period
λ⊙ = 223 − 248◦ (November 6–30). We find a further detection in the automatic analysis, yielding a radiant near ϑ Leonis at α = 166 ◦. 0, δ = 14 ◦. 4 with
V∞ = 71 km/s at λ⊙ = 253◦ (December 5) which exactly fits the extrapolated Leonid drift. This apparent
‘appendix’ of the Leonids can be traced over eight bins
(251◦ –258◦) with a well detectable VR between 1.3 and
2.8. Perhaps the Leonids extend further than usually
expected.
4 GEM (Geminids): this strong shower has a
rather short activity period with a steep descending
branch after the peak at λ⊙ = 261 ◦. 5. We find VR ≥ 2.0
for 242–264◦, i.e. December 4–16. Two bins at either
sides still allow to trace the radiant, but the number of
shower meteors becomes very small.
15 URS (Ursids): activity is detectable in the interval λ⊙ = 266◦ − 272◦ . Outside this interval, VR is
< 0.7 (0.6 in the two preceeding bins, 0.4 in the two
consecutive bins). Due to the unique position, the radiant is clear and consistent over the period 266–272◦.
10 QUA (Quadrantids): we find VR ≥ 0.9 in
the entire interval λ⊙ = 274 − 292◦ , but similar to the
Orionids and as discussed above, the data yield a consistent radiant over the period λ⊙ = 281 − 290◦. The
narrow peak occured at slightly different positions over
the decade and therefore the high rate occurs in more
than one Solar longitude interval (Figure 8). Furthermore, the rate ‘tail’ after the peak lasts for another
four bins to 288◦ with VR ≥ 2.5 and thus more than
three times the detection threshold. Visual data yield
ZHR ≥ 5 for 281◦ –286◦ and thus also a longer tailing
activity than preceeding the maximum (Rendtel & Arlt,
2009; pp. 126–128).
6.2
107
Established minor showers
The analysis should also allow to detect meteor showers of low activity. First, we look at the ‘established
minor showers’. Of course, the category does not say
anything about the strength of the source as compared
to the other showers in the MDC list. The automatic
analysing procedure indeed provides us with all detectable showers which are in reach of the cameras, although
the coverage of the southern hemisphere is much poorer
than the northern section. We applied the same limiting factors for the detection as derived from the analysis
of the outer regions of the major showers where these
essentially are sources of small activity. The results are
summarized in Table 3, the activity profiles are shown
in Figure 9 and 10. Further, we comment on details of
the showers in the text.
145 ELY (η-Lyrids): we find a clearly defined radiant despite the low activity over the period λ⊙ =
46 − 53◦ which is almost exactly coinciding with the
entry in the MDC list (see Table 3). The drift of the
radiant as found from our data is shown in Figure 11.
Our data show a smooth VR-profile (see Figure 9) with
a maximum rate of VR = 2.1 at λ⊙ = 50◦ . Before 49◦
and after 52◦ , the rate is low with values of VR < 1.
The agrees well with the activity profile of this shower
which was recently included in the IMO’s working list
(Arlt & Rendtel, 2006).
1 CAP (α-Capricornids): the radiant of this
shower is quite close to the ecliptic and therefore interferes with radiants of the Antihelion Source. The major
difference is the velocity which is close to 30 km/s for the
Antihelion meteors and 24 km/s for the α-Capricornids.
The radiant is obvious in the interval between λ⊙ =
109◦ and 138◦ . Although considered as a minor shower,
the activity reaches a maximum VR = 5.2 at λ⊙ = 125◦
and remains above 1.0 for all but the very last bin.
12 KCG (κ-Cygnids): this is another shower with
a very low activity. We find VR ≥ 0.8 in the entire
period λ⊙ = 135◦ − 146◦ with a weak maximum of
VR = 1.5 at λ⊙ = 141◦ (profile in Figure 9). The radiant is well defined from 134◦ to 146◦ with increasing
scatter towards the begin and end of the activity period
(Figure 12). The entry in the MDC list gives values
for the returns in 1993 and 2007 as well as an annual
(average?) value. The radiant positions deviate significantly: the 1993 and 2007 radiants are by 5 ◦. 3 off in
declination alone. Since our data sample includes data
of 10 years, a sharp radiant position is not to be expected. Our analysis of short appearances (section 6.5)
reveals another radiant at α = 288 ◦. 2, δ = +58 ◦. 6 in
four bins (149◦ –152◦ ). The declination fits well with
the 2007 data, but the maximum VR is detected only
at λ⊙ = 152◦ , while the 2007 maximum was observed
11◦ earlier. This shows that the κ-Cygnids behave more
like a complex than like a single well defined shower.
206 AUR (Aurigids): this is the first shower of a
series of further sources in the Auriga-Perseus region occurring from end-August to October. This established
shower is known for its outbursts. The VR is not high
because only the 2007 outburst was recorded by a few
WGN, the Journal of the IMO 37:4 (2009)
6.0
6.0
5.0
5.0
4.0
4.0
VR
VR
108
3.0
2.0
1.0
3.0
2.0
1.0
1 CAP
0.0
0.0
110
115
120
125
130
135
2 STA
170
180
Solar Longitude (J2000)
200
210
220
230
Solar Longitude (J2000)
2.0
5.0
4.0
VR
1.5
VR
190
1.0
3.0
2.0
0.5
1.0
12 KCG
0.0
16 HYD
0.0
134
136
138
140
142
144
146
245
250
Solar Longitude (J2000)
255
260
265
Solar Longitude (J2000)
5.0
1.5
1.0
3.0
VR
VR
4.0
2.0
0.5
1.0
18 AND
17 NTA
0.0
0.0
210 215 220 225 230 235 240 245 250 255
225
230
Solar Longitude (J2000)
5.0
2.5
4.0
VR
VR
2.0
1.5
3.0
1.0
22 LMI
19 MON
0.0
256
258
260
262
204
264
206
210
212
214
3.0
32 DLM
2.0
3.0
VR
VR
208
Solar Longitude (J2000)
Solar Longitude (J2000)
5.0
4.0
245
2.0
1.0
0.0
240
Solar Longitude (J2000)
3.0
0.5
235
2.0
1.0
1.0
0.0
145 ELY
20 COM
260
270
0.0
280
290
300
Solar Longitude (J2000)
310
46
47
48
49
50
51
52
53
Solar Longitude (J2000)
Figure 9 – Activity profiles for the showers labelled as ‘established’ in the MDC list derived from our video data, sorted
by the MDC shower numbers.
WGN, the Journal of the IMO 37:4 (2009)
5.0
4.0
4.0
3.0
3.0
VR
VR
109
2.0
2.0
1.0
1.0
206 AUR
191 ERI
0.0
0.0
132
134
136
138
140
142
144
146
155
156
Solar Longitude (J2000)
157
158
159
160
161
162
Solar Longitude (J2000)
3.0
4.0
3.0
VR
VR
2.0
1.0
2.0
250 NOO
1.0
208 SPE
0.0
0.0
162
164
166
168
170
230
235
Solar Longitude (J2000)
240
245
250
Solar Longitude (J2000)
1.0
2.0
VR
VR
1.5
0.5
319 JLE
1.0
0.5
331 AHY
0.0
0.0
280
281
282
283
284
285
Solar Longitude (J2000)
280
282
284
286
288
Solar Longitude (J2000)
Figure 10 – Activity profiles for the showers labelled as ‘established’ in the MDC list derived from our video data sorted
by the MDC shower numbers.
Figure 11 – Radiant of the η-Lyrids derived from our video
data.
Figure 12 – Radiant of the κ-Cygnids derived from our video
data.
cameras of the Network. The last one before this happened in 1994.
208 SPE (September ε-Perseids): is the second
shower of the series mentioned before. The VR reaches
2.6 and remains above 2.0 over five successive bins. It
should be emphasized that the radiant obtained from
the video data (48 ◦. 0, +39 ◦. 5) differs significantly from
the position (60◦ , +47◦ ) given in the IMO working list
(Arlt & Rendtel, 2006). The position listed in the MDC
files is 50 ◦. 2, +39 ◦. 4.
191 ERI (η-Eridanids): well detectable activity
with a peak VR = 4.9 (Figure 10) and a consistent
radiant drift fitting the position given in the list of established showers of the MDC.
2 STA (Southern Taurids) / 17 NTA (Northern Taurids): the two branches of the Taurids are
110
WGN, the Journal of the IMO 37:4 (2009)
Figure 13 – Radiant of the Leonis Minorids derived from
the video data.
often assumed to coincide in their activity period with
weak maxima separated by about two weeks. Our analysis as well as previous studies based on video and visual
data show that the situation is somewhat different. The
southern branch can be found much earlier, starting at
λ⊙ = 165◦ and lasting to 237◦ ; the northern branch can
be detected from 206◦ to 258◦ . The STA maximum at
λ⊙ = 197◦ reaches a VR = 5.7 and is higher than the
value of 4.1 found for the NTA at λ⊙ = 231◦ . The maxima are thus separated by 34◦ in Solar longitude. The
dip in VR near λ⊙ = 236◦ is not real but an artefact
due to the strong Leonid activity at that time.
22 LMI (Leonis Minorids): this is another shower which is active during the Orionid period. It produces rates which are clearly above the background.
The radiant and activity is well defined from λ⊙ = 203◦
to 214◦ (Figure 13) and the maximum VR = 4.2 occurs
at λ⊙ = 210◦ .
18 AND (Andromedids): the annual Andromedid shower is a very weak source which can be traced
over almost a month. There is no other source interfering with the shower meteor data because of their distinct very low velocity.
250 NOO (November Orionids): only few shower compilations include this weak shower which we can
trace from λ⊙ = 233◦ to 254◦ . It shows a well defined
radiant as well as an activity VR ≥ 1.5 for most of the
period (see Figure 10). The highest VR = 3.2 occurs at
λ⊙ = 248◦.
16 HYD (σ-Hydrids): this is a minor shower with
a reasonably high activity over several bins. We find
VR ≥ 4 in five consecutive bins from 253◦ to 258◦ and
a maximum VR = 4.7 at λ⊙ = 254◦ , also in good agreement with long-term visual results yielding an average
maximum ZHR of about 3 (Rendtel & Arlt, 2009). The
radiant is well defined from 244◦ to 269◦ with a slight
deviation against the listed position of ∆α = −4◦ and
∆δ = +2◦ at the maximum date. The dip in VR near
λ⊙ = 262◦ is not real but an artefact due to the strong
Geminid activity at that time.
19 MON (December Monocerotids): except
the maximum date, all parameters coincide with the
listed values. However, the activity is very low and has
no pronounced maximum. Our highest VR = 2.5 occurs
at 256◦ and thus 4◦ earlier than the catalogue date. The
radiant can be traced until λ⊙ = 268◦ , but the rates are
below our threshold in the bins at 266◦ and 267◦ .
319 JLE (January Leonids): the activity is just
below the detection limit and if there were not the entry
in the MDC list, we would not have not taken the detection as a signature of a shower. Since its rate remains
below the threshold, we do not present an VR-profile
here. However, the derived data of the radiant and velocity fit well with the tabulated values.
331 AHY (α-Hydrids): another established shower with an activity very close to the detection limit. The
shower was found automatically from 284◦ onwards,
while the earlier activity was found when we checked
for short duration showers. Probably the dominating
Quadrantid activity caused that the minor source became undetectable. As in the case of the 319 JLE, the
parameters fit well.
Perseus-Auriga-showers in September and
October: we clearly detect showers in the PerseusAuriga region from end-August to early October. These
include the established shower 206 AUR (Aurigids) and
208 SPE (September ε-Perseids) which have been shortly discussed in the Section 6.2. Further examples are the
β-Aurigids (210 BAU) and the October δ-Aurigids
(224 DAU), both having ‘working status’. Especially
the relation between the 208 SPE and 224 DAU has
been analysed in previous papers (Rendtel 1993; Dubietis & Arlt, 2002). However, there is a larger number
of showers detectable from this region which requires a
more detailed analysis. Therefore we list only the two
‘established’ sources here.
20 COM (Comae Berenicids) / 32 DLM (December Leonis Minorids): this special case needs
to be discussed in some detail. The Comae Berenicids (COM) have been in most shower compilations over
many years. Recently, an analysis of video data (Molau,
2006) gave no hint at the existence of a radiant at the
position listed in the IMO shower list as well as in the
MDC list. The same analysis yielded a source which is
obviously about 15◦ west of the radiant given for COM.
Our present analysis shows that there are two sources
(see the profiles shown in Figure 9). Weak activity from
the ‘old’ radiant listed as Comae Berenicids (20 COM)
can be detected in the period 260–271◦ (December 12–
23), but definitively not longer. The other source which
was clearly found already in the previous analysis is detectable over a much longer interval 253–315◦ (December 5 – February 4). The latter produces higher rates –
we find a maximum VR = 4.6 at λ⊙ = 268◦ . This radiant perfectly fits the position given for the December
Leonis Minorids (32 DLM) in the MDC list on December 14 (λ⊙ = 262◦ ), although our analysis yields the
maximum activity on December 20 (λ⊙ = 268◦ ). The
20 COM is listed as an ‘established shower’ while the
32 DLM is in the working list.
The question is why this confusing situation occurred. Much of the past information is based on visual data and rather few photographs. Probably, most
WGN, the Journal of the IMO 37:4 (2009)
111
of the activity was observed around the Geminid maximum (≈ 262◦) and shortly thereafter, i.e. close to 268◦
(December 20) when both sources are detectable. Meteors occuring later are scarce and in most cases a reliable
radiant determination is not possible. Another reason
for uncertainties of the radiant position is the distribution of the observed meteors around the radiant. Meteors are observable mostly west and north of the radiant, which is the case especially before local midnight.
Hence the position remains unreliable and two possible
radiants cannot be distinguished because these are almost on one line. So it could easily be possible that
both the existence of two radiants and the ceasing activity from the Comae Berenicids was not correctly observed. The conclusion from our analysis is clear: there
Figure 16 – Radiant of the ε-Geminids derived from the
are two showers. We find 20 COM for 260–271◦ (De- video data.
cember 12–23) and the other, slightly stronger 32 DLM
in the period 253–315◦ (December 5 – February 4).
232 BCN (Daytime β-Cancrids): interestingly,
this shower can be seen in our video data. The right
6.3 MDC showers with working list sta- ascension and the velocity fit well with the data of the
MDC list, but the declination is by 9◦ off, probably due
tus
The main achievement of the data set analysed here is to the fact that we can detect only very few meteors in
the possibility to confirm the existence of showers with the twilight period appearing to one side of the radiant.
MDC working list status and to refine their parameters
(radiant position and drift, velocity). Furthermore, we
derive information about the video rate VR and thus
of the activity period. This was not available for most
of the showers compiled in the MDC working list. A
summary of our results is listed in Table 4 and the VRprofiles are shown in the Figures 14 and 15. Details
for selected cases are described in the text. It must be
emphasized that these are all weak sources, often close
to the detection limit. As described above, sections of
the showers which remain below the thresholds set in
the beginning have been omitted. Since the radiant
data strongly depend on the number of associated meteors per bin, the drift values remain uncertain in some
cases.
136 SLE (σ-Leonids): the radiant is found both
in the standard analysis and the manual check for short
period meteor activity. Although the VR is just at the
detection threshold we listed it here, because the velocity of the meteors is very low and thus the source should
be easily distinguishable from the background.
190 BPE (β-Perseids): the data seem to fit the
entries in the MDC list quite well. However, the radiant
drift is quite uncertain with jumps in consecutive bins.
Either the sample is strongly affected by the Perseids
with their radiant about 13◦ north, or the entire radiant
is an artefact due to mis-aligned Perseids. Interestingly,
the radiant is not found in SonotaCo’s list based on
orbit determinations.
23 EGE (ε-Geminids): this entry of the working
list is quite similar to the established κ-Cygnid shower
with low rates and no obvious maximum. The EGE
rates are above 2 over the entire activity period. Slightly
enhanced rates occur between λ⊙ = 206◦ and 209◦ (Figure 14), coinciding with the Orionid maximum period.
From Figure 16 it is obvious, that the radiant drift is
well defined from 203◦ to 215◦.
6.4
New radiants found from the Network data
Many of the new radiants have been found in the months
July and August. This is mainly due to the enormous
amount of observational data. Over several years, the
collection summarizes a substantial number also from
weak sources.
409 NCY, ν-Cygnids: this weak source produces
a radiant about 30◦ east of the Lyrids. We carefully
checked that these are not Lyrids which are sorted out
from the major shower because they may have occurred
far away from the radiant. Such meteors could produce
a radiant further east with apparently slightly slower
meteors. The substantial sample, the consistent radiant
data found over the entire period and the large distance
to the Lyrids radiant clearly indicate an independent
source.
410 DPI, δ-Piscids: the video rate VR exceeds
2.5 over the entire detection period, and the radiant
drift is well defined. The radiant fits a (backwards)
extrapolated drift of the July-Pegasids and the meteors
have a similar velocity (67 km/s for JPE, 70 km/s here).
However, the shower identified as July-Pegasids (see discussion in section 6.3) is significantly weaker than the
source producing this activity. Therefore we propose
this as a new radiant rather than the continuation of
the July-Pegasids. It might be a similar case as we find
it with the series of radiants in the Perseus-Auriga region in September-October.
411 CAN, c-Andromedids: the radiant (32◦ ,
+49◦ ) is about 30◦ east of the (extrapolated) Perseid
radiant on July 13. At this time, the activity of the
Perseids is negligible, so that an interference with erroneously mis-identified and ‘shifted’ Perseids can be
excluded. Of course, the similarity of the velocities
(59 km/s) requires caution. The radiant drift shows
WGN, the Journal of the IMO 37:4 (2009)
Table 4 – Data of meteor showers included in the MDC working list, sorted by Solar longitude (J2000.0). The MDC list does not give an activity period for the showers of this list –
so this is a new information derived from our analysis.
Shower
40
136
343
175
184
190
197
337
234
226
333
237
23
241
232
333
339
336
334
ZCY
SLE
HVI
JPE
GDR
BPE
AUD
NUE
EPC
ZTA
OCU
SSA
EGE
OUI
BCN
OER
PSU
KDR
DAD
ζ-Cygnids
σ-Leonids
h-Virginids
July Pegasids (*)
γ-Draconids
β-Perseids
Aug. Draconids
ν-Eridanids
Oct. ε-Piscids
ζ-Taurids
Oct. Ursae Majorids
σ-Arietids
ε-Geminids
Oct. Ursae Minorids
Dayt. β-Cancrids
o-Eridanids
ψ-Ursae Majorids
Dec. κ-Draconids
Dec. α-Draconids
Peak λ⊙ [◦ ]
(V)
(L)
16
31
32
108
125
135
148
164
196
203
202
206
206
211
214
232
253
251
253
20
28
39
107
125
135
142
168
195
196
202
202
206
208
213
235
253
250
257
Period λ⊙ [◦ ]
(V)
7– 23
28– 35
32– 35
105–126
120–127
132–143
138–156
161–181
194–198
199–204
199–206
200–210
203–214
206–214
212–221
231–238
247–261
248–254
252–264
Radiant position and drift [◦ ]
α
∆α
δ
∆δ
V∞ [km/s]
(V)
(L)
299.9
202.9
214.1
347.2
280.9
44.6
275.6
66.7
1.2
79.7
143.8
50.7
101.8
273.4
110.5
60.2
168.3
185.4
203.6
43.5
20.0
24.1
68.1
27.3
67.4
23.3
67.7
19.2
60.6
53.0
45.5
70.4
27.5
65.1
27.1
61.1
42.9
43.8
112
(*) JPE: velocity drift observed −0.16 km/s per 1◦ in Solar longitude
+0.5
+1.2
−1.3
+0.9
−0.2
+0.9
+0.6
+0.6
+0.3
+0.8
+1.9
+1.1
+0.9
−1.1
+0.8
+0.2
+1.5
+0.6
+0.8
+40.2
+4.7
−11.4
+11.1
+50.7
+40.7
+62.3
−0.5
+14.0
+12.2
+63.3
+22.1
+28.2
+74.3
−6.1
−1.3
+43.1
+71.5
+60.1
+0.3
−0.2
−1.6
+0.2
+0.2
−0.5
+0.1
+0.5
+0.9
−0.8
−0.2
0.0
−0.2
−0.3
+1.2
−0.2
−0.3
−1.2
−0.3
40.6
25.5
21.8
62.3
28.5
67.1
20.6
66.8
24.4
68.1
55.2
42.0
68.8
32.9
67.0
29.1
61.7
44.8
43.1
Max.
VR
Data
Met.
1.6
0.7
1.6
1.6
1.6
2.8
1.1
5.1
0.8
0.8
2.5
1.0
2.8
0.8
3.4
1.2
1.8
2.5
1.7
402
269
192
591
428
1176
951
1185
210
294
533
475
1134
308
386
229
432
225
531
113
4.0
2.0
3.0
1.5
VR
VR
WGN, the Journal of the IMO 37:4 (2009)
2.0
1.0
1.0
0.5
23 EGE
40 ZCY
0.0
0.0
203
205
207
209
211
213
8
10
Solar Longitude (J2000)
12
14
16
18
20
22
Solar Longitude (J2000)
1.0
2.0
VR
VR
1.5
0.5
136 SLE
1.0
0.5
175 JPE
0.0
0.0
28
30
32
34
105
110
Solar Longitude (J2000)
115
120
125
Solar Longitude (J2000)
2.0
3.0
VR
VR
1.5
1.0
2.0
1.0
0.5
184 GDR
190 BPE
0.0
0.0
120
121
122
123
124
125
126
132
134
Solar Longitude (J2000)
138
140
142
1.0
1.0
VR
1.5
VR
1.5
0.5
0.5
226 ZTA
197 AUD
0.0
0.0
199
138 140 142 144 146 148 150 152 154 156
4.0
201
202
203
204
1.5
3.0
VR
1.0
2.0
1.0
200
Solar Longitude (J2000)
Solar Longitude (J2000)
VR
136
Solar Longitude (J2000)
0.5
234 EPC
232 BCN
0.0
0.0
212
214
216
218
Solar Longitude (J2000)
220
194
195
196
197
198
Solar Longitude (J2000)
Figure 14 – Activity profiles for the showers of the ‘working list’ derived from our video data, sorted by the MDC shower
numbers.
114
WGN, the Journal of the IMO 37:4 (2009)
1.5
1.0
VR
VR
1.0
0.5
0.5
237 SSA
241 OUI
0.0
0.0
200
202
204
206
208
210
206 207 208 209 210 211 212 213 214
Solar Longitude (J2000)
Solar Longitude (J2000)
3.0
2.0
2.5
1.5
VR
VR
2.0
1.5
1.0
0.5
1.0
0.5
334 DAD
333 OCU
0.0
0.0
199
200
201
202
203
204
205
206
252
254
Solar Longitude (J2000)
256
258
260
262
264
Solar Longitude (J2000)
3.0
6.0
5.0
VR
4.0
VR
2.0
1.0
3.0
2.0
1.0
336 KDR
0.0
337 NUE
0.0
248
249
250
251
252
253
254
162 164 166 168 170 172 174 176 178 180
Solar Longitude (J2000)
Solar Longitude (J2000)
1.5
2.0
1.5
VR
VR
1.0
0.5
1.0
0.5
338 OER
339 PSU
0.0
0.0
231
232
233
234
235
236
237
238
248
250
252
254
256
258
260
Solar Longitude (J2000)
Solar Longitude (J2000)
2.0
VR
1.5
1.0
0.5
343 HVI
0.0
32
33
34
35
36
Solar Longitude (J2000)
Figure 15 – Activity profiles for the showers of the ‘working list’ derived from our video data, sorted by the MDC shower
numbers.
WGN, the Journal of the IMO 37:4 (2009)
115
Table 5 – Data of meteor showers found in the IMO Video Meteor Network data, sorted by Solar longitude (J2000.0).
The activity data expressed in terms of the video rate (VR) described above is summarized in Figure 17.
Shower
409
410
411
412
413
414
73
415
81
416
417
418
NCY
DPI
CAN
FOP
MUL
ATR
ZDR
AUP
SLY
SIC
ETT
BHE
ν-Cygnids
δ-Piscids
c-Andromedids
f-Ophiuchids
µ-Lyrids
α-Triangulids
ζ-Draconids
August Piscids
September Lyncids
Sep. ι-Cassiopeiids
η-Taurids
β-Herculids
Max. (λ⊙ )
[◦ ]
Period (λ⊙ )
[◦ ]
30
92
110
98
116
120
122
132
167
169
211
324
28– 44
89– 93
102–114
96–100
113–118
119–124
122–126
130–137
165–172
166–171
211–221
322–326
some ‘irregular’ jumps near λ⊙ = 100 − 102◦ while it
is smooth after this date until 114◦ . The VR varies
around 2 with a maximum at λ⊙ = 110◦ , i.e. July 13,
which coincides approximately with the onset of the
‘regular’ Perseids. We give 103–114◦ as the activity
period because of the inconsistent early position mentioned above; if this were not the case, we could trace
the radiant back to λ⊙ = 96◦ .
412 FOP, f-Ophiuchids: this source is very weak
and thus close to the detection limit. The low velocity
of the shower meteors at 21 km/s should remarkably
decrease the effect of accidentially aligned sporadic meteors. Particularly at the end of the detection period,
after λ⊙ = 104◦ , the scatter of the radiant position becomes larger than the limits set for our study. Hence
we give an activity period λ⊙ = 99 − 104◦.
413 MUL, µ-Lyrids: the radiant at 273◦ , +39◦ ,
could also be named ϑ Her. This very weak source is
another case with a peculiar low V∞ = 23 km/s. As in
the case of the f-Ophiuchids, there are no other sources
in a wider surrounding region of the sky. The radiant
drift is not well defined, but the position is at about 62◦
ecliptical latitude.
414 ATR, α-Triangulids: like in September with
the Perseus-Auriga showers, there may be more than
one source in the vicinity of the (north) apex region
in July. The July-Pegasids have been described in the
previous section. Meteors from this radiant in Triangulum are found at 71 km/s. An effect from other known
sources is not expected because the other radiants are
far enough from the radiant.
73 ZDR, ζ-Draconids: this radiant is another
case formed by slow meteors at 25 km/s coming from almost 70◦ ecliptical latitude. Like the other two sources
with similar low velocity meteors, the video rate VR
remains close to the detection limit over the entire period. The drift is not well defined towards the end of
the given period. A shower designated as ZDR was
already listed in the MDC list. The stored data of radiant position and velocity are based on Lindblad (1971).
In this work, two orbits were identified. Similar (slow)
meteors give further radiants in Hercules and Cygnus.
Jenniskens (2006, p. 712) lists two, the 88 ODR and
182 OCY at 116 and 117◦ , respectively. The low veloc-
Radiant position and drift [◦ ]
α
∆α
δ
∆δ
305.2
10.9
32.4
266.4
273.1
28.9
261.7
7.5
107.4
36.7
55.5
246.0
+1.8
+0.3
+1.0
+4.0
−0.0
−0.2
+5.8
+0.9
+1.7
−0.2
+0.9
+0.9
+39.4
+5.5
+48.4
+8.5
+39.4
+28.1
+67.8
+18.3
+55.0
+65.0
+23.7
+23.5
+0.7
+0.4
+0.4
−0.6
−0.5
−2.2
+0.8
+0.1
+0.3
+1.0
−0.0
−0.9
V∞
[ km/s ]
VR
Data
Met.
42
71
59
21
23
71
25
66
61
50
47
55.5
1.8
4.2
2.3
0.7
0.6
3.6
0.6
1.1
1.4
0.8
1.2
1.4
508
105
491
81
129
192
148
433
467
278
323
99
ity is common to all these entries. The shower identified
from our video data is new and indeed near ζ Draconis. Hence it was decided in the Task Group on Meteor
Shower Nomenclature (Jenniskens et al., 2009), to keep
the existing code and to use the new data obtained from
this analysis.
415 AUP, August Piscids: this source might
have some similarity to the α-Triangulids discussed before. The radiant is about 15◦ north of the ecliptic and
the velocity of the meteors is rather high (66 km/s). We
can trace the radiant for some more days than listed
here, but the uncertainties of the position become quite
large after λ⊙ = 138◦ .
81 SLY, September Lyncids: this shower may
be associated with others radiating from the PerseusAuriga region in autumn with similar velocities, such as
AUR, SPE or DAU. This radiant is the northernmost
found in the region. The radiant can be consistently
traced over the entire period from 165◦ to 172◦ . Two
earlier bins at 162 and 163◦ also show the radiant with
similar strength, but with an uncertain radiant drift.
The entry of the 81 SLY also goes back to Lindblad’s
(1971) paper and the shower data is based on very few
graphically reduced photographic orbits. Like in the
case of the 73 ZDR, the Task Group proposed to keep
the code for the shower but to replace the data with
those obtained from our video meteor analysis. Further
details are discussed in Section 6.4.
416 SIC, September ι-Cassiopeids: we find this
shower at α = 34◦ , δ = +65, with V∞ = 50 km/s in a
rather short period around λ⊙ = 169◦ . Interferences
from other known sources can be excluded.
417 ETT, η-Taurids: in the interval λ⊙ = 211 −
221◦ (Max. 211◦ ), we detect the radiant at α = 54◦ , δ =
+24◦ ; V∞ = 47 km/s, near η Tau. Actually, the analysis yields two detections, which obviously define one
radiant near the Pleiades with a reliable video rate and
a well defined radiant.
418 BHE, β-Herculids: is a shower found from
the short activity period check (see Section 6.5). It can
be found between λ⊙ = 322 and 326◦ . This is a period
with a generally low meteor activity and thus suited for
the detection of weak sources. The VR of 1.4 is well
above the threshold value.
116
WGN, the Journal of the IMO 37:4 (2009)
4.0
2.0
VR
VR
3.0
2.0
1.0
1.0
409 NCY
410 DPI
0.0
3.0
0.0
28
30
32
34
36
38
40
42
44
2.0
88
89
2.0
90
91
92
93
VR
VR
412 FOP
1.0
1.0
411 CAN
0.0
102
2.0
0.0
104
106
108
110
112
114
4.0
99
100
101
102
103
104
105
3.0
VR
VR
413 MUL
1.0
2.0
1.0
0.0
113
2.0
114
115
116
117
414 ATR
0.0
119
120
2.0
118
121
122
123
124
VR
VR
73 ZDR
1.0
1.0
415 AUP
0.0
122
2.0
0.0
123
124
125
126
127
130
2.0
132
134
136
138
VR
VR
416 SIC
1.0
1.0
81 SLY
0.0
166
0.0
VR
2.0
164
166
168
170
172
167
168
169
170
Solar Longitude (J2000)
171
172
1.0
417 ETT
0.0
210
212
214
216
218
Solar Longitude (J2000)
220
222
Figure 17 – Activity profiles of the new showers found from the video data. The vertical lines indicate the limits of the
activity period defined by the VR and the radiant position. The graphs are sorted as in Table 5.
Shower
43
136
149
337
81
323
97
101
ZSE
SLE
NOP
NUE
SLY
XCB
SCC
PIH
ζ-Serpentids
σ-Leonids
N. May Ophiuchids
ν-Eridanids
Sept. Lyncids
ξ-Coronae Borealids
South. δ-Cancrids
π-Hydrids
Peak and period λ⊙ [◦ ]
(V) (L)
(V)
4
23
52
165
186
295
298
319
365
28
50
168
185
295
296
317
3– 7
21– 24
47– 53
162–165
186–189
290–295
294–298
315–319
Rad. position, drift (V) [◦ ]
α
∆α
δ
∆δ
256.2
199.5
237.1
74.7
110.2
248.3
131.5
215.2
+2.1
−0.5
+1.6
+0.6
−2.9
−0.2
+1.7
+1.0
−4.1
+3.6
−8.2
+0.3
+48.4
+29.2
+10.6
−26.2
+0.4
−0.6
+0.9
−1.9
−0.7
−0.1
−1.0
−1.9
Radiant (L)
α
δ
266.3
192.6
249.0
68.7
110.0
244.8
134.1
210.3
−6.3
+3.1
−14.0
+1.1
+47.9
+31.1
+10.1
−23.0
V∞ [km/s]
(V)
(L)
63.8
22.7
28.0
67.0
67.7
50.1
28.7
69.7
68.4
25.6
30.0
66.8
66
45.7
27.6
71.6
Max.
VR
Data
Met.
1.5
1.1
1.8
3.7
1.6
1.2
0.9
3.2
86
129
291
157
237
105
134
88
WGN, the Journal of the IMO 37:4 (2009)
Table 6 – Showers of short duration which were detected only in 3–4◦ intervals of Solar longitude according to the described manual refinement. (V) refers to the results from our
video data, (L) to the MDC list.
117
118
6.5
WGN, the Journal of the IMO 37:4 (2009)
Short duration showers
The standard procedure as decribed above requires a radiant to be detected over five degrees in Solar longitude.
Consequently, it omits short duration showers, such as
the Draconids. In order to find active sources which
are detectable over a shorter period of time, we run
an additional analysis allowing for a minimum of three
degrees length only. Of course, many known sources
re-appeared and several unreliable sources showed up,
which is why we concentrated only on strong sources
or those fitting to showers from the MDC list. Overall, nine additional sources have been detected, among
these one new source, named 418 BHE (β-Herculids;
see Section 6.4). The results from the short interval
analysis are summarized in Table 6.
The procedure finds radiants which fit the data of
the Northern May Ophiuchids (149 NOP) reasonably
well in two separate intervals. Both radiants differ from
the listed position, and the velocity fits better in the
second period (λ⊙ = 47◦ − 53◦ ) which is included in
Table 6.
81 SLY is found not only in the short interval listed
in Table 6 but was detected automatically by the standard procedure. This procedure reveals the SLY in two
periods (179◦ –184◦ and 189◦-194◦ ) with an interruption
in the center. The radiant is close to the apex, which is
also detected as a relatively strong source in this interval. Hence we expect an interference from apex meteors leading to an uncertain radiant position of the weak
September Lyncids. Consequently, we list the shower
only in the central short interval in which the fit with
the listed data is best and VR = 1.6. A recent discussion in the Task Group (Jenniskens, 2009) as well
as the analysis of our data set yielded a likely connection between the 81 SLY as they were included in the
existing MDC list on the one hand and our new detection (now the 81 SLY as described in the Section 6.4
and Table 5) and the short-duration activity discussed
here on the other hand. However, the fact that our
analysis yielded two detections (the ‘new’ radiant and
the slightly deviating short duration shower) indicates,
that the case is not yet completely solved. At the moment, we cannot match all detections to describe one
continuous source. We either see one source at different
activity intervals or more than one shower (with similar physical data) being part of the already mentioned
complex in the Perseus-Auriga region. Details will be
presented in the respective upcoming analysis.
6.6
Established showers from the MDC
list not found in our data
Many, but not all showers that are marked as established in the MDC list were found in our analysis. There
are several reasons why a shower may have been missed.
(i) The shower is too weak or occurs at a time of
year that is poorly covered by observations. Chances
for this are low, because our total sample has a good
coverage of the entire year.
(ii) The activity interval of the shower is too short,
or the shower is not permanently active: We will have
missed showers, which show only once in a few years
significant activity or who are active for only one or
two days. AMO and JBO are such showers.
(iii) The radiant lies far south. Most meteor observations were obtained from the northern hemisphere.
There is also a subset of about 15 000 meteors recorded
from Australia, but in general the coverage of the southern hemisphere is poor. The geographical distribution
of the cameras should allow to detect all significant meteor showers north of δ ≈ −25◦. ‘Established’ showers
south of this limit are ACE, BHY, GNO, PHO, PUP,
and PPU.
(iv) The meteors are too faint to be detected by
video. If meteor showers were detected by radar, they
might be composed of meteors beyond the limit of video
observation.
(v) The meteors occur at daytime. Most daytime
meteor showers cannot be detected in the optical domain.
Several established MDC list showers were missing
in our analysis. So we checked the original radiant set
of the analysis per Solar longitude bin whether we find
traces of these showers.
102 ACE (α-Centaurids): no traces of this far
southern radiant, but our sample includes only few respective data.
11 EVI (η-Virginids): radiant is clearly visible in
our data. As it is close to the antihelion source, we have
not listed this shower separately here. Another shower,
123 NVI (Northern March Viginids), has essentially the
same position but a lower velocity. Our data fits the
11 EVI.
27 KSE (κ-Serpentids): in the interval 14–16◦
we find weak radiants which could fit the KSE data.
λ⊙ =14◦: 230 ◦. 5, +12 ◦. 5, 43 km/s; λ⊙ =15◦ : 227 ◦. 4,
+12 ◦. 5, 45 km/s; λ⊙ =16◦: 221 ◦. 8, +17 ◦. 5, 47 km/s.
21 AVB (α-Virginids): in our analysis we find one
weak detection in the region which does not fit well.
It is located at 197◦ , −6 ◦. 5, V∞ =20 km/s at 29◦ Solar
longitude.
137 PPU (π-Puppids): not found in our analysis
due to its southern position and the low activity except
its outbursts.
55 ASC (α-Scorpiids:) this is another radiant
which is near the Antihelion source. Our analysis yields
two detections at 54◦ and 55◦ which are more than
10◦ northeast at 256◦ , −23 ◦. 5 and correspond to V∞ =
37 km/s.
61 TAH (τ -Herculids): no signs in our analysis.
165 SZC (Southern June Aquilids): could be a
very short duration shower. At λ⊙ = 79◦ find a radiant
at 302 ◦. 8, −33 ◦. 5, V∞ = 35.0 km/s which fits the listed
values reasonably. The next two bins also show a radiant close to the position (304◦ , −34◦ ) but composed of
meteors with 45 km/s.
164 NZC (Northern June Aquilids): can be
detected in our results, although the routine matched
our data with the 179 SCA (σ-Capriconids). Both are
not too far from the Antihelion source.
WGN, the Journal of the IMO 37:4 (2009)
63 COR (Corvids): V∞ = 14.4 km/s – meteors at
such very low velocities should be easily distinguished
from the background, but the analysis yields no sign
of this shower. During the observed years there was
obviously no activity present.
170 JBO (June Bootids): is found only as an
extremely weak detection at λ⊙ = 97◦ (229 ◦. 5, +43 ◦. 5,
V∞ = 18.0 km/s). As found in other analyses, the
activity is essentially zero outside the outburst intervals.
187 PCA (ψ-Cassiopeiids): despite the position
far from other sources and not interfering with activity
periods of other showers, nothing is found in our data.
183 PAU (Piscis Austrinids): we find weak signs
earlier between 113 and 117◦, but the data remained
below our thresholds for shower detection.
3 SIA (Southern ι-Aquariids): is difficult to separate from the strong 5 SDA. The analysis gives radiants in the vicinity of the SDA over the activity period,
espcially at 127◦ and 130◦, but no consistent radiant
which could be identified as SIA.
198 BHY (β-Hydrusids): lacks from the small
amount of data for this far southern radiant.
233 OCC (October Capricornids): nothing is
found in our data.
281 OCT (October Camelopardalids): radiant
α = 168 ◦. 3, δ = +78 ◦. 0, V∞ = 44.5 km/s at λ⊙ = 192.9◦
is clearly visible between 192 and 193◦ , but not found
by the automatic procedure because of the very short
activity interval. The maximum video rate is VR = 2.0
and thus above the thresholds (based on 118 meteors).
9 DRA (October Draconids): the radiant α =
262◦ , +56◦ , V∞ = 19 km/s at λ⊙ = 195 ◦. 5 is detected
between 195 and 196◦ , but the duration is too short
for the automatic procedure. The maximum video rate
is VR = 0.8 (only 80 meteors as the sample does not
include any period of enhanced activity).
246 AMO (α-Monocerotids): this is an established shower which cannot be found in our analysis.
It is famous for its short-lived outbursts of which the
last was observed in 1995. In all other years, the rates
remained close to the detection limit. Our data show
signs of a very weak AMO activity. However, the radiant deviates from the outburst position in right ascension and declination. Actually, the analysing procedure
yields two radiants on both sides of the known position
with the more northern one producing a higher rate
(maximum VR = 2.7 at 238◦ ). Furthermore, we find
the best fitting velocity deviates by −3 km/s for the
radiant south of the listed position, but +4 km/s for
the radiant north of the listed position. This indicates
some artefacts, possibly due to uneven distribution of
associated shower meteors around the radiant position.
254 PHO (Phoenicids): lacks from the small
amount of data for this southern radiant.
256 ORN (Northern χ-Orionids: is part of the
Antihelion source and continues the Southern Taurid
activity. The analysis detects the radiant, but we do
not analyse it here separately.
Not unexpectedly, the daytime (D.) showers 141
DCP (D. χ-Piscids), 144 APS (D. April Piscids), 153
OCE (Southern D. ω-Cetids), 171 ARI (D. Arietids),
119
172 ZPE (D. ζ-Perseids), 173 BTA (D. β-Taurids), 188
XRI (D. ξ-Orionids) and 221 DSX (D. Sexantids) did
not occur in our analysis.
7
Summary and Conclusions
As summary, we show two figures that present all meteor shower radiants detected in the IMO Video Meteor
Database in a sinusoidal projection with right ascension on the abscissa and declination on the ordinate
(Figure 18). The meteor shower velocity is color coded.
It is worth to compare the plot with the presentation
of the Japanese results in SonotaCo (2009), Figure 5
and back cover of the respective WGN issue. All significant features are found in both plots. Note, however, that the plots are created in slightly different ways.
From double-station data like the SonotaCo analysis, a
unique radiant point (right acsencion, declination, velocity) is obtained for each individual meteor recorded
by two or more stations. Hence, each dot represents a
single meteor in their graph. From single station data as
presented here, the radiant position is ambiguous: For
each meteor, there are several possible radiant points
with different positions and velocities along the backward trace. Only when large data sets are analysed in
a statistical way, we find radiant points composed by
several meteors. These radiant points are depicted in
Figure 18, i.e. here each dot represents approximately
50 single station meteors on average, with a range between 10 and 10 000. Meteor showers show up as cluster
of points in the SonotaCo plot, but they would get lost
in our graph because even thousands of meteors are represented by a single dot. For this reason, we coded the
meteor number with the brightness: the brighter a dot,
the more meteors contributed to the radiant.
Figure 19 is our version of the corresponding Figure 6 in the SonotaCo paper. Here, the abscissa represents the difference between the ecliptical radiant longitude and the solar longitude, and the ordinate the ecliptical latitude of the radiant. The similarity of both plots
is amazing and underlines the abilities of the method
presented here.
Recent radiant searches (SonotaCo, 2009; Brown et
al., 2008, 2009) gave not only new positions of shower
radiants but increased also our knowledge about the
physical parameters and the extensions of the streams.
The list of nine major and 44 minor showers analysed
here show that the procedures work well. Cross-comparisons also demonstrate that the results obtained from
independent data sets and applying different methods
reveal consistent and therefore reliable results. Hence
the detection of twelve new showers is not surprising.
Further, the shift in velocity over the activity period
found here and confirmed for several examples from
SonotaCo’s independent data sample demonstrates that
the continuous collection of data is not only useful for
an increasing accuracy of existing data but also for new
results.
120
WGN, the Journal of the IMO 37:4 (2009)
Figure 18 – Distribution of radiants detected in the IMO Video Meteor Database over right ascension and declination in a
sinusoidal projection. The brightness of each spot represents the number of meteors that contributed to the radiant, and
the meteor shower velocity is coded in the color (reproduced on the back cover).
Figure 19 – Distribution of radiants detected in the IMO Video Meteor Database in Sun-centered ecliptical coordinates
with the ecliptical radiant longitude minus the solar longitude as x-axis, and the ecliptical latitude as y-axis.
WGN, the Journal of the IMO 37:4 (2009)
8
Acknowledgements:
We are in debt of all video camera operators (see Table 1) who provide us with their meteor data on a regular basis and lay the foundation for analyses like this.
Even if the observation is largely automated these days,
it still requires a lot of passion and patience to set up
a video system, get used to the analysis software, operate one or even multiple cameras for several years and
process the data before they are collected in the central
database.
In particular, we like to thank the Japanese meteor
observer, UFO* programmer and meteor network operator SonotaCo. In recent years, we could establish vivid
contacts between the networks and learn a lot from each
other and together in cooperation. The SonotaCo network provides us with the unique chance to check our
findings with an independent dataset, just as we can
provide further evidence to findings of the SonotaCo
network. For this paper, SonotaCo provided us with
the radiant plots (Figure 18 and 19). He confirmed the
variation of meteor shower velocities that we detected,
and provided fruitful discussions and valuable input for
the meteor shower lists.
121
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authors.